1. Field of the Invention
The invention is directed to a strip reel for winding up metal strips to form a coil and winding off metal strips from a coil, respectively, in such a way that the edges are aligned, particularly for winding a rolled hot strip, comprising a driven reel mandrel which is supported so as to be rotatable, substantially comprising a mandrel body, segments and spreading bar, wherein the reel mandrel can be spread in the radial direction by the spreading bar, which is movable axially in the mandrel body, with the intermediary of a coupling and a rotating drive.
2. Description of the Related Art:
In order to wind up or unwind strip-shaped material, e.g. a hot-rolled or cold-rolled steel strip, a strip reel with spreadable reel mandrel is conventionally provided. However, such strip reels are exposed to every kind of unfavorable operating condition, e.g. high speeds, cantilever beam loads, heat, water and centrifugal force, all of which greatly impede the performance or the operating behavior of the reel and cause high maintenance costs. A typical reel for winding up a hot strip in hot strip rolling mills is consequently dynamically and thermally loaded to an extremely high degree, since hot strips with a strip thickness of e.g. 25 mm or a strip width of e.g. 2100 mm must be wound to form a coil weighing up to 45 t at 200,000 strip entries per year. The strength of the different construction elements of the reel and its maintenance capacity must therefore be carefully taken into account.
A strip reel having the basic design principle according to the construction type described in the beginning is known from DE-PS 32 41 870. For the purpose of winding up metal strips to form a coil and winding off metal strips from a coil, respectively, in such a way that the edges are aligned, this strip reel, which is already known, comprises devices for displacing the coil transversely relative to the strip running direction during the winding and unwinding, which devices are constructed in such a way that a readjustment of the coil is effected relative to the running strip edge in that the winding shaft is supported in a machine column so as to be axially displaceable and is guided out of the machine column on the side opposite the winding mandrel and placed on a mounting gear unit which is connected with the drive motor via a universal-joint shaft which compensates for movement. The particular problems to be taken into account when winding hot strips are not addressed in the strip reel known from DE-PS 32 41 870.
Reel mandrels for hot strip reels are generally moved, according to the present state of the art, with after-spreading. After-spreading means that the reel mandrel is closed during the strip entry and is spread subsequently to approximately 90% of the spreading amount only after one to three windings. A reliable grasping of the first windings and a faster build-up of strip tension is achieved by means of this manner of movement. The actuation of the spreading movement is effected by means of a rotating hydraulic cylinder, wherein the command for actuating the hydraulic cylinder is effected automatically by means of determining the distance of the strip tip. Although the reliability of the control devices has constantly been improved over the course of time, it cannot be avoided absolutely that the after-spreading movement of the reel mandrel is not effected and the coil is wound on a closed mandrel. Since the reel mandrel can usually not be closed further in this situation, there have been substantial problems in removing the wound coil, which weighs several tons, from the reel mandrel, since the coil sits too tightly on the reel mandrel. Therefore, it has been suggested in a reel arrangement to loosen the coil from the reel mandrel by switching the rotating direction of the reel mandrel. The tightly wound coil should accordingly open in a helical manner in order to release the winding mandrel. The mandrel can subsequently spread, the coil can be tightened and removed after the spreading of the mandrel. This procedure can result in damage to the strip so that the coil must be scrapped.